When compressed vertex positions are used in a blend shapes mesh, we
need to make sure we set the w-component of the position vector to 1.0
When octahedral compression is used on normals/tangents, they need to be
converted to cartesian floats to be used for blend shapes
This conversion also changes the number of components of that vertex
attribute, which caused issues because previously there was an
assumption that you had the same number of components in the blend shape
buffer as you did in the original mesh's buffer (which is not true for
oct norm/tang)
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